Art of converting high boiling hydrocarbon oils into lower boiling hydrocarbon oils



JuIy 23, 1935. R. E. WILSON 2,9,367

ART OF CONVERTING HIGH BOILING HYDROCARBON OILS INTO LOWER BOILINGHYDROCARBON OILS Filed June 1, 1931 Patented July 23, 1935 UNITED STATESPATENT OFFICE.

I i 2,009,367 r Y ART OF CONVERTING-HIGH BOILING HY- DROCARBON OILS nvroLOWER BOILING HYDROCARBON OILS Robert E. Wilson, Chicago, Ill.,'assignor to Standard Oil Company, Whiting,'Ind., a corporation ofIndiana Application June 1, 1931,"Seria1 No. 541,516

5 Claims (01. 19666) The present invention relates to the conversion ofrelatively high boiling hydrocarbon oils into relatively low-boilinghydrocarbon oils, for example oils suitableas fuel for internalcombustion engines. The present invention is particu larly directed toimprovements in such conversion operation conducted undersuperatmospheric pressure conditions.

In certain of such operations, the oil is raised to and maintained atcracking temperature and under a relatively'high superatmosphericpressure for a predetermined period of time. Theoil is then passed intoa zone of substantially lower pressure wherein a substantial portion ofthe conversion products, with the exception of the heavy tan-likeresidues, is vaporized by the contained heat of the oil. The tarryresidues are withdrawn from the system and the vapors are subjected tofractional condensation whereby the constituents heavier than thosedesired in the distillate product are condensed and separated from thedesired low boiling products, such higher-boiling portions, if desired,being returned, along with fresh stock, to the original crackingoperation.

In accordance with the present invention, the oil is brought to andmaintained at cracking temperature and under a relatively highsuperatmospheric pressure for a predetermined period of time, as in theabove type of operation, and is then subjected to successive pressurereducing stages under controlled conditions, whereby a number ofadvantages are secured, asmore fully pointed out hereinafter. v

Referring more in detail-t0" the drawing, th numeral 5 indicates avalved line leading from any suitable source of hydrocarbon oil which isto be converted into lower boiling hydrocarbon oils. The oil is suppliedthrough line Sunder pressure by any suitable means, for example, a pumpnot shown), and is passed through a coil 6 in the upper portion of afractionating column 1, wherein the oil is partially heated by hotvapors in the column. The oil passes from coil 8 into a line 8 providedwith valvedbranch-pipes 9 and I0. Branch-pipe 9 leads to a coil I lmounted in the upper'portion of a flash chamber l2 and branch-pipe l0leads to a coil [3 mounted within the upper portion of an evaporatorchamber l4. Thus, all the oil being fed into the system may be passed toeither of the coils II and I3, or closely controlled portions of it maybe fed simultaneously to coils l l and 13. The oil from coil l3 passesthrough line |5 into a second coil l6 mounted below coil l3 in the upperportion of evaporator chamber I4. Trap-out plates H and !8 are providedin the evaporator chamber i below coils I 3 and I6, respectively. Theoil after passing through coils I3 and 16, passes into a line l9 leadingto a lagged stock supply or .mixing drum 20 and the oil from coil llpasses into a line 2! which is connected to the line l9. Oil fed to coilII in tower l2 and to coils I3 and IS in tower I4 is thus againcollected,'after preheating, in line [9 and mixing drum 20.

In drum 2B the preheated fresh stock is admixed with hot oil productsintroduced therein through lines l9, 33 43 and 41, as will behereinafter described. A preheated mixed or composite feed stock isthus-collected in the drum 2!).

A line 22 leads from the bottom of mixing drum 2!] to a hot-oilpump 23,by which the hot composite feed stock from drum 20 is forced throughline ?2 to a heating coil ZA-suitably mountedin a combustionfurnaceshown diagrammatically at 25. The heated oil is brought to thedesired cracking temperature in coil 24 and then passes through line 26to a reaction chamber or soaking drum 21, the line 26 being preferablycon'nected to one end of the chamber 21. During" its pas-.

sage through coil 24,the oil is'heated to cracking or conversiontemperature, under a high super atmospheric pressure, for example, above450 lbs., and preferably750 to 900 lbs., and fiowsat a velocitysufficient toavoid substantial deposition of coke withinthe coil 24.The" highly heated products discharged from coil 24 into chamber 21 aremaintained therein'at cracking temperature and under 'superatmosphericpressure, ap-

proximately that at the coil outlet, for example,

a temperature of 875 F. and a pressure of 750 lbs. may be maintained inthe chamber 21. The highly heated productsare passed from the other endof the chamber'through a line 28 pressure lower than that'maintained inthe reaction chamber 21, but in general exceeding lbs; gauge. Forexample'a pressure of from to 225 lbs; may be; maintained in chamber [4,a preferred range being from 'to 200 lbs.'- Under these conditions, asubstantial vaporization of light products takes place, but at a highertemperature (above 735'F., preferably above 750 F. and at which crackingtakes place at a s'ubstantial rate) and' with a lower proportion ofvolatilized products heavier .than .the desired low-boiling productsthan in operation as hitherto practiced, wherein the cracked productswere separated at reduced pressurs'of, say 60 lbs. or lower At the sametime, the unvaporized liquid or tar, being of lighter grade, may bemaintained at the higher temperature prevailing, at which crackingoccurs without excessive or disturbing carbonization.

The separated vapors ascend the tower M and come into intimate contactwith downflowing reflux; whereby any heavy entrained constituents areremoved. This reflux which contains heavier constituents of the vaporsis condensed therefrom by the cooling action of the fresh stock flowingthrough coils l3 and i6, and collects on the trap-out plates I l and I8from which any portion of the condensate may overflow into the lowerportion of the evaporator tower. The amount of such condensate whichoverflows may be closely controlled by withdrawing predeterminedportions of the condensate collected on the trap-out plates I l and I8through valved lines 33 and 34, respectively. The condensate sowithdrawn from plates H and I8 through lines 33 and 34 is passed throughline 33* to the drum 20 where it is mixed with the other constituents ofthe feed stock supplied to the coil 24 in the manner already described.Ordinarily it is preferred to effect condensation of vaporous productsabove the plate I! which are lower boiling than those condensed aboveplate l8 and below plate ll, the resulting heavier condensate on plateI3 being permitted to overflow plate l8 and the resulting lightercondensate on plate [1 comprising substantially clean stock which ispassed to the composite stock tank 20. The heavier condensate thuspermitted to overflow plate 18 functions to remove entrainment from thevapors in the por tion of tower-I4 below plate l8.v The portion of thetower l4 below the trap-put plate l8 may be provided with a plurality ofelements (not shown) for effecting intimate contact of the vapors andliquid therein and removing entrained matter from the vapors, such asbaiile plates, screen plates, ring and disk plates, or the like. Thelatter plates have the advantage of less tendency to coke up. s f

The remaining, vapors are passed from the upper end of tower l4, througha valved line 32, to the lower portion of the fractionating'column 7wherein they are fractionated, to separate the constituents heavier thanthose desired in the low-boiling product or gasoline.

The separated unvaporized liquid or tar is removed from the bottom ofevaporator tower l4 through line 30 provided with a suitable pressurereducing valve 30, and passes through one of the valved branch lines 3|into thev low-pressure flash chamber, or tower, l2. A lowsuperatmospheric or approximately atmospheric pressure is maintainedwithin the tower l2, whereby substantially all but the heavy residualconstituents of the liquid or tar, passed th'e'reinto from tower H isflashed into vapors by'the contained heat of such products, the flashedvapors constituting desirable chargingfstock for a cracking operationwherein, low-boiling oils, such as gasoline, are produced. For example,the tower l2 may be maintainedunder atmospheric pressure, or slightlythereabove, say from 1 to 30 lbs. gauge. The interior of the tower 12may be provided with a plurality of baflle elements 35 for eifectingintimate contact between ascending vapors and de scending liquidtherein, which maybe similar to those provided within the tower M. Theheavy residue is withdrawn from the bottom of tower l2, and from thesystem, through a valved line 31. The flashed vapors ascend the towerlZiand come into intimate contact with cooler down- 7 charged through avalved line 42.

flowing liquid whereby any entrained tarry residues may be removedtherefrom. This cooler liquid may comprise certain heavy fractionscondensed from the vapors by the cooling action of the coil i i throughwhich is passed the relatively cool fresh stock, as already described.

The vapors pass out of the upper end of tower 12, through a valved line38 to a condenser 39, wherein they are condensed. The condensate,together with any uncondensed vapors or gases, passes from condenser 39through a line 40 to a separator drum 4| wherein the liquid condensateand vapors or gases separate, the latter being dis- 7 The condensate isdrawn from separator 4 I, through a valved line 33, by pump 43 andforced to the mixing drum 5% and/or through pipe line 43 into the upperportion of tower M at a point above plate 57. Thus, any portion of thecondensate from separator 4i may be permitted to overflow the plate H tofunction as a reflux medium for the portion of column 44 therebelow. Thefractionated vapors, supplied to column 7 from tower I4,

pass out of the top of column I through a valved line 19 to a condenser50, wherein they are condensed. The condensate formed in condenser 50,together with any remaining vapors or gases, passes from condenser 50through line 5! to a separator 52. The condensate, which is the desiredpressure distillate product, is withdrawn from separator 52, and fromthe system, through a valved line 53 which may lead to a suitablestabilizing operation or to a gas release tower connected to anabsorption plant, before going to storage. The gas which at thispressure is practically free of any constituents desired in thedistillate product, is withdrawn from separator 52 through a line 54connected to valved lines 55 and 56. The line 55 leads from the systemand the branch-line leads to the lower portion of the second flash towerl2, whereby all or any portion of the gases may be introduced into thebody of liquid residue products therein to aid in stripping therefromthelower-boiling constituents.

The condensate formed in the column! is withdrawn from the, bottom ofthe column I through line 47 by pump 48 and forced to the mixing drum20. Low-boiling hydrocarbons, desired in the gasoline distillate, arestripped from the condensate within column, '1 by means of steamadmitted through 47 or by other means. The necessary cooling in theupper portion of column 1 may be effected in whole, or in part, by thepassage of fresh feed stock through coil 6. If desired, additionalcooling may be effected by passing a cooling mediumthrough coil 44.

I Any vapors given ofi within the mixing drum 20 may be withdrawntherefrom and passed through valved vent line 5! into tower 14,preferably the upper portion thereof.

Steam, or other inert gas, may be introduced into the liqiud in thelower portion of flash chamber 12 instead of the gases from separator52; However, since these gases are under a relatively high pressure ithas been found that they are capable of effecting the desired strippingof the heavy tar residues in the bottom of chamber 12 and hence it ispreferred to so employ them.

In a specific operation, gas oil having a gravity of 29.4 Be. wascharged into the system through linei;

' In the operation of the process, for example, with a gasoil crackingstock and-with a temperature in the reaction chamber 21 of approximately875 F. and a pressure of about 750 lbs.,

the unvaporized liquid or tar in the evaporator l4 may be maintained ata temperature of 750 to 825 F. and under a pressure of 125 to 150 lbs.,the liquid in tower l4 having a gravity of 10 tov 12 A. P. I. Underthese conditions, of pressure and temperature, additional cracking iseffected in the body of tar in tower M at a substantial rate, butwithout disadvantageous coke formation. With similar stock andheating-conditions, but

with lower pressures, below lbs. for example,

in the evaporator tower M, a much heavier tar forms therein under veryconsiderably lowertemperatures, say 700 to 715 F., under whichconditions no substantial cracking occurs, or'if the temperature of thetar body were raised, serious and disadvantageous coking Would occur.

.. Under the conditions above set forth for operation in accordance withthe present invention, the

vapors are released in the evaporator tower M at substantially highertemperature, 750 .to 825 F., or higher, and are hence available tosecure a higher temperature or" preheating in the feed stock passedthrough the coils I3 and I6, and also in the reflux condensateswithdrawn through the lines 33 and 3 5, and, as a result, the compositefeed stock in the feed tank 28 is maintained at substantially highertemperatures, say 35 to 50 F. higher than with lower pressure prevailingin the evaporator tower. M, as in prior practice. Furthermore, theadditional cracking taking place in the tarry body in the evaporator l4results in the formationof additional vaporizable constituents, whichare released when the tar is discharged into the flash tower i 2, andthese additional light constituents are made available for cracking orcondensation in the condenser 39 and return to the composite feed tank25. Although these advantages are secured, at the same time, theconditions prevailing in the evaporator tower l are suo that the refluxcondensate condensed therein and returned to the composite feed tank 29is likewise at a somewhat higher temperature than has been the case inprior-practice.

The operation of the evaporator 14 and the fractionating column I may beso controlled as to secure a condensation of constituents heavier thanthe desired products in the upper portion of the tower I t, and acondensation and stabilization of the desired products in thefractionating column I.

It will be apparent that the details of the apparatus and process as setforth hereinbefore may be materially modified within the scope of theinvention, and are not intended to be regarded as limitations upon thescope of the invention, except as set forth in the accompanying claims.

I claim:

1. The method of converting higher boiling hydrocarbon oils into lowerboiling hydrocarbon oils which comprises heating such oil to a temperature of at least 850 F. while maintaining it under asuperatmospheric pressure of at least 750 lbs. per square inch, passingthe highly heated oil to a zone of substantially lower superatmosphericpressure of at least lbs. per square inch wherein the desiredlow-boiling products together with a portion of the products heavierthan the desired products are vaporized by the contained heat of the oiland the unvaporized products are maintained at a temperature of at least750 F., separately withdrawing the vaporous and unvaporized products,passing the unvaporized products from said low pressure zone to anotherzone of still lower pressure wherein substantially all of the remainingheavier constituents thereof desirable as cracking stock are vaporizedby the contained heat of the said prodthe uncondensed constituentsthereof through the unvaporized product in said second-named lowpressure zone before the' latter is withdrawn therefrom.

.2. The method of converting higher boiling hydrocarbon oils into lowerboilinghydrocarbon oils which comprises heating such oil to atemperature of at least 850 F. while maintaining it under asuperatmospheric' pressure of at least 450 lbs. per square inch, passingthe highly heated oil to a zone of substantially lower superatmosphericpressure of at least 100 lbs. per square inch wherein the desiredlow-boiling prbducts together with a portion of the products heavierthan the desired products' are vaporized by the contained heat of theoil and the unvaporized products are maintained at a temperature of atleast 750F., separately withdrawing the vaporous' and unvaporizedproducts, passing the unvaporized heavier products from said lowpressure zone to another zoneof still lower. pressure whereinsubstantiallyall of the remaining heavier constituents thereo'fdesirableas cracking stock are vaporized by'the contained heat' of the saidproducts, separately withdrawing the vaporous and unvaporized portions,subjecting th vaporous products from said second-named low pressure zoneto a condensing operation, passing the resulting condensate to the oilundergoing cracking, and passing a portion of the vapors from saidfirst-named low pressure zone through the unvaporizedproduct in saidsecondnamed low pressure zone before the latter product is withdrawntherefrom.

3. The method of converting higher boiling hydrocarbon oils into lowerboiling hydrocarbon oils which comprises heating such oil to atemperature of at least Z50" F. while maintaining it under a highsuperatmospheric pressure, passing the highly heated oil to a zone ofsubstantially lower superatmospheric pressure of at least 100 lbs. persquare inch wherein the desired lowboiling products together with aportion of the products heavier than the desired products are vaporizedby the contained heat of the oil and the unvaporized products aremaintained at a temperature of at least 750 F., separately withdrawingthe vaporous and unvaporized products, passing the unvaporized productsfrom said low pressure zone to another zone of still lower pressurewherein substantially all of the remaining heavier constituents thereofdesirable as cracking stock are vaporized by the contained heat of thesaid products, separately Withdrawing the vaporous and unvaporizedportions, subjecting the vaporous, products from said second-named lowpressure zone to a condensing operation, passing the resultingcondensate to the oil under going cracking,subjecting the vapors fromsaid first-named low pressure zone to a condensing operation, andpassing the uncondensed constituents thereof through the unvaporizedproduct in said second-named low pressure zone before the latter productis withdrawn therefrom.

4. The method of converting higher boiling hydrocarbon oils into lowerboiling hydrocarbon oils which comprises heating such oil to atemperature at least 850 F. while maintaining it under asuperatmospheric pressure of at least 750 pounds per square inch,passing the highly heated oil to a zone of substantially lowersuperatmospheric pressure of at least lbs. per square inch wherein thedesired low-boiling products together with a portion of the productsheavier than the desired products are vaporized by the contained heat ofthe oil and the unvaporized products are maintained at a temperature ofat least 750 F., separately withdrawing the vaporous and unvaporizedproducts, passing the unvaporized products from said low pressure zoneto another zone of still lower pressure wherein substantially all of theremaining heavier constituents thereof desirable as cracking stock arevaporized by the contained heat of the said products, separatelywithdrawing the vaporous-and unvaporized portions, subjecting thevaporous products from said second-named low pressure zone to acondensing operation, passing the resulting condensate to the oilundergoing cracking, subjecting the vapors from said first-named lowpressure zone to a fractionating operation wherein the heavierconstituents thereof are condensed as reiuX condensate, subjecting thefractionated vapors to a com densing operation, and passing theuncondensed constituents thereof through the unvaporized product in saidsecond-named low pressure zone before the latter is withdrawn therefrom.

5. The method of converting higher boiling hydrocarbon oils into lowerboiling hydrocarbon oils which comprises heating such oil to atemperature of about 900 F. while maintaining it under asuperatmospheric pressure of about 750 lbs. per square inch, passing thehighly heated oil to a zone of substantially lower superatmosphericpressure of at least 100 lbs. per square inch wherein the desiredlow-boiling products together with a portion of the products heavierthan the desired products are vaporized by the contained heat of the oiland the unvaporized products are main tained at notless than 750 F.,separately withdrawing the vaporous and unvaporized products, passingthe unvaporized products from said low pressure zone to another zone ofstill lower pressure wherein substantially all of the remaining heavierconstituents thereof desirable as cracking stock are vaporized by thecontained heat of the said products, separately withdrawing the vaporousand unvaporized portions, subjecting the vaporous products from saidsecond-named low pressure zone to a condensing operation, passing theresulting condensate to the oil undergoing cracking, subjecting thevapors from said firstnamed low pressure zone to a fractionatingoperation wherein the heavier constituents thereof are condensed asreflux condensate, passing said reflux condensate to the oil undergoingcracking, subjecting the fractionated vapors to a condensing operation,and passing the uncondensed constituents thereof through the unvaporizedprod uct in said second-named low pressure zone before the latter isWithdrawn therefrom.

ROBERT E. WILSON.

